Sir Anthony O'Reilly was one of two Irishmen to receive a full knighthood the New Year's Honours list. A Dublin-born businessman, Mr David McMurtry, was also named.
Sir David, an engineer, built up Renishaw, a company which makes machines for measurement and received the award for his "services to design and innovation". His investiture was in early March.
Before this year the last Irish citizen to receive a full noble title was Cork-born Baroness Detta O Cathain in 1983, according to the Department of Foreign Affairs.
She received an OBE for her work as adviser to the Tories on agriculture as head of strategic planning with the Milk Marketing Board. In 1991 she was made a life peer and was given the title of Baroness. Since her award she has worked as director of the Barbican Theatre in London, and has held non-executive directorships at British Airways, Tesco and Sears.
Other notable Irish knights include Sir Roger Casement, who was knighted in 1911 following a report he compiled highlighting atrocities against native labourers by white traders in the Putumayo river region of Peru.
The Dublin-born unionist, Sir Edward Carson, received a knighthood in 1900 for his work as a barrister.
Sir Charles Gavan Duffy, nationalist and founder of The Nation newspaper, who was involved in land reform agitation in the 19th century, received the award after he moved to Australia and entered politics. He was knighted in 1873 for services to the colony.
Sir Hugh Lane received his knighthood in 1909 for his services to art in Ireland, while Sir Horace Plunkett, founder of the agricultural co-operative movement, also was knighted.